NEW YORK, Nov 29 (Reuters Health) -- New brain research on rats may help
scientists understand human conditions ranging from Parkinson's disease to
addictive disorders, according to a report published in the November 26th issue
of the journal Science.
Dr. Ann Graybiel, of the Massachusetts Institute of Technology in
Cambridge, led an international team of researchers in studying the changes that
take place in the brain as a new habit is acquired. They hope that their
findings will help them understand what goes wrong when humans have trouble
learning or stopping patterns of behavior.
"Patients with Parkinson's disease seem to suffer from defects in learning
procedures or habits," Graybiel pointed out in an interview with Reuters Health.
"Then there's a whole other group (of conditions), including obsessive
compulsive disorder and Tourette's syndrome, in which there is too much activity
-- like in obsessive compulsive disorder when patients perform a behavior over
and over again."
The researchers used a new technology that allowed them to record activity
in the brains of rats continuously, using several electrodes. While the rats
learned a maze task, the scientists monitored nerve cells in the basal ganglia,
the area of the brain thought to be responsible for learning and performing
routine behaviors.
The animals were trained to run through a maze, turning either left or
right at a certain point when they heard a tone. When the rats were learning the
routine, about half of the nerve cells in the basal ganglia responded in a
particular pattern, and most of these responses occurred at the time of the
right or left turn.
As the rats became more experienced with the maze, however, the patterns
of brain activity changed dramatically. The nerve cells responded mostly to the
beginning and end of the maze routine and were much less active in between.
The study results fit in with the idea that the brain uses "templates," or
stored behavioral routines, that are triggered by an event and then "run"
automatically, the researchers say. They think that when a new habit is learned,
nerve cell responses in the brain are reorganized.
Graybiel explained that she and her group want to help people with
conditions such as Parkinson's disease by pinpointing where the reorganization
of nerve cell responses goes wrong.
The research team has already started a new project looking at the links
between brain activity in the basal ganglia and brain activity in the cerebral
cortex, which is responsible for higher learning processes.
The investigators are also studying drug addiction in rodents, which
respond to addictive drugs by developing stereotyped patterns of behavior that
may show patterns similar to those described in the current study.
